Medicinal plant species have been used by the ancestors around the world since ancient times. Rosmarinus officinalis is one of the most used medicinal plants, which belongs to the family Lamiaceae. To investigate the effects of different levels of salinity stress along with the induction of bacterial growth stimulation on the amount of essential oil composition in R. officinalis, an experiment was conducted in a randomized complete block design with 12 treatments and five replications. Salinity treatments included 0 (control), 2.5 (T1), 5 (T2), 7.5 (T3), 10 (T4) and 12.5 (T5) NaCl g/L, and the bacterium was pseudomonas fluorescence. The percentage of essential oils showed a significant relationship with increasing salinity either alone or in composition with plant growth-promoting rhizobacteria (PGPR) inoculation treatments and it increased with increasing salinity levels to treatment 4 (T4, 10 g/L NaCl) but decreased with further increases in salinity levels in treatments without using PGPR and it was constant in treatment with using PGPR. Phellandrene, one of the main compounds of essential oils, showed a trend like the whole amount of essential oils in both group of treatments. Abiotic and biotic factors may influence the different mechanisms and limit the interactions between plant and beneficial bacteria, resulting in less-than-acceptable performance in plant growth promotion and management of diseases. In this context, the results revealed that the application of PGPRs can help improve the essential oil yield in R. officinalis even in salinity conditions.

In this study, we investigated the chemical composition, the antibacterial activity, and the antioxidant properties of extracts obtained from the leaves, flowers, and fruits of Eucalyptus largiflorens F. Muell. The antioxidant effects of the methanolic extract of aerial parts of the plant, obtained by Soxhlet apparatus, were estimated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and β-carotene/linoleic acid methods. The essential oils were chemically characterized by gas chromatography (GC) coupled with mass spectrometry (MS) and flame ionization detector (FID). Thirty compounds were identified, with 1,8-cineol, α-pinene, aromadendrene, globulol and α-phellandrene being the major components. The antibacterial activities of the essential oils were tested against several bacterial isolates, including Staphylococcus aureus, Staphylococcus epidermidis and Escherichia Coli, using the disc diffusion method. All the essential oils exhibited antibacterial activity. The maximum zone of inhibition was observed for Escherichia coli, with the fruit essential oil in the concentration (100 μL). There was no significant antioxidant activity in the essential oils, while the extracts exhibited considerable antioxidant effects in comparison to butylated hydroxytoluene (BHT). In this regard, the flower extract showed the highest antioxidant activity in both DPPH (IC50 = 21.5±0.2 μg/mL) and β-carotene/linoleic acid tests (Inhibition (%) = 84.3±0.7). Finally, the fruit essential oil exerts a significant antibacterial activity against several bacterial strains and exhibits a significant antioxidant effect in the β-carotene/linoleic acid tests, thus it may represent an innovative nutraceutical tool able to act on bacteria and host oxidative stress related to infections.

Background: Environmental factors and biological regulators have effects on plants morpho-physiological and phytochemical charecteristics. Objective: The aim of this study was to investigate the growth and yield of Rosmarinus officinalis in coexistence with plant growth-promoting rhizobacteria (PGPR) under purified urban wastewater. Method: This study was done in research greenhouse of ...